City of Virginia Beach Uranium Mining Impact Study Energy Advisory Committee September 29, 2011
Uranium Mill Tailings Original Concept –119 million # of uranium (0.06% ore) • 100 million pounds of yellow cake • Open-Pit, 76 MCY of tailings Dec 2010 plan – 60 million # of uranium (0.11% ore) • 50 million pounds of yellow cake • Deep Shaft, 20 MCY of tailings • About 1/3 returned to mine shafts, 2/3 stored in 8 surface tailings impoundments • Surface tailings impoundments will be 40 acres (maximum) and store about 1.5 – 2.0 MCY, each Mount Trashmore in Virginia Beach is 20 acres and 1.3 million cubic yards
Project Description Coles Hill
Near PMP Storms in Virginia Examples: • Nelson County – August 1969 27 – 31 inches in 8-hours (Hurricane Camille) • Madison County – June 1995 30 inches in 14 hours
Virginia Beach Disaster Simulation Study Model and estimate the water quality impacts from a storm-based breach of a uranium mill tailings confinement structure, which results in a large release of mill tailings downstream to the Banister or Roanoke Rivers Provide the results to the National Academies of Sciences Committee on Uranium Mining for consideration as part of its study due Dec 2011
Study Qualifiers The study simulated a rare event that regulations are supposed to prevent Conservative Worst Case Scenario based on above ground impoundments The model does not address the issue of whether there will be a catastrophe – it only simulates the outcome if one did occur
Aftermath of a Tailings Release Tailings separate into particulate (80-90%) and dissolved (10-20%) components Particulates tend to remain above Kerr Dam – in the reservoirs, river beds and flood plains Dissolved contaminants tend to move downstream with the water and flow into and then out of Kerr Reservoir, into and then out of Lake Gaston, thru Roanoke Rapids Reservoir, and ultimately downstream
Impacts From a Tailings Release Radioactivity in the water is initially very high, but declines as the particulates settle and the dissolved contaminants flow downstream Radioactivity of the sediments remains high on a long-term basis Subsequent high flows re-suspend some settled particulates and move them incrementally downstream – much smaller effect Most particulates will remain in the flood plain, river beds, or reservoirs upstream of Kerr Dam
Fate of Radiological Contaminants in the System after One Year Banister River, Various Roanoke River, Various Modeling Scenarios Modeling Scenarios Percent of Radioactivity 5-11% 11-19% Leaving the System (Flowing Downstream as a Dissolved Contaminant) Percent of Radioactivity 0-2% 0-2% Remaining in the Water Column Percent of Radioactivity 89-93% 78-87% Remaining in the System (In the Flood Plain, River Bed or Kerr Reservoir)
Radioactivity Concentration in the Water Column from Radium-226 and Thorium-230 Banister + Dam 15m + CSW3 50% + HYD2 1% + GSC1 + RAD2 50 Radioactivity Concentration (pCi/L) 45 40 35 30 Node 286 - At Mouth of Kerr Reservoir 25 Node 397 - At Kerr Dam MCL for Combined Radium-226 and 228 20 15 10 5 0 0 50 100 150 200 250 300 350 400 Time (Day) Radioactivity Concentration in the Water Column from Radium-226 and Thorium-230 Roanoke + Dam 15m + CSW3 50% + HYD2 1% + GSC1 + RAD2 100 Radioactivity Concentration (pCi/L) 90 80 70 60 Node 311 - At Mouth of Kerr Reservoir Node 420 - At Kerr Dam 50 MCL for Combined Radium-226 and 228 40 30 20 10 0 0 50 100 150 200 250 300 350 400 Time (Day)
Model Limitations – Flushing Time Kerr Reservoir was modeled as a large, one- dimensional channel – a giant river Reasonable during flood periods. During normal and drought periods, Kerr Reservoir will act more like a lake Dissolved contaminants will experience mixing, dispersion, stagnation. May add to flushing time Lake Gaston has a volume equal to about half of Kerr Reservoir which will add to flushing time
Flushing Time in Kerr and Gaston Retention time for Kerr and Gaston combined: About one month during severe flooding About six months during normal flows About one year during droughts It can take one or two retention times to completely flush dissolved/suspended contaminants from a large water body Depending upon whether it is wet or dry following a contamination event, it could take two months or two years to flush dissolved and suspended contaminants from both reservoirs
Conclusions – Phase 1 If there is a storm-based release of tailings, the particulates will settle in the river and reservoir beds, dissolved contaminants will move downstream Radiation in the water column rises significantly then will subside River and reservoir beds are significant long-term trap for particulates which are the bulk of tailings Impacts upstream of Kerr Dam are greater and potentially longer lasting than downstream
Impact Study – Phase 2 2D model for Kerr and Gaston 1996 (Hurricane Fran): 100-year storm in Banister River, 30-50 year storm in remainder of Basin, followed by 2002 drought year Second lowest impoundment level (15 M) More precise data on tailings properties (radiation, grain size distribution, partition coefficients) Study is behind schedule – Current target is for end of the year
Kerr Reservoir 1D Channel Model
Kerr Reservoir: 2D Model Grid
Lake Gaston: 2D Model Grid 59 blocks
Radioactivity Concentration in the Water Column from Radium-226 and Thorium-230 Banister + Dam 15m + CSW3 50% + HYD2 1% + GSC1 + RAD2 50 Radioactivity Concentration (pCi/L) 45 40 35 30 Node 286 - At Mouth of Kerr Reservoir 25 Node 397 - At Kerr Dam MCL for Combined Radium-226 and 228 20 15 10 5 0 0 50 100 150 200 250 300 350 400 Time (Day) Radioactivity Concentration in the Water Column from Radium-226 and Thorium-230 Roanoke + Dam 15m + CSW3 50% + HYD2 1% + GSC1 + RAD2 100 Radioactivity Concentration (pCi/L) 90 80 70 60 Node 311 - At Mouth of Kerr Reservoir Node 420 - At Kerr Dam 50 MCL for Combined Radium-226 and 228 40 30 20 10 0 0 50 100 150 200 250 300 350 400 Time (Day)
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